DecisionLog for EMFMetricPublisher added (#5717)

* DecisionLog for EMFMetricPublisher added

* decisionLog for emfMetricPublisher added

* decisionLog for emfMetricPublisher added

docs/design/core/metrics/emf-metric-publisher/DecisionLog.md

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+# Decision Log for AWS SDK for Java v2 EMFMetricPublisher
+
+
+## 11/19/2024
+
+**Source:** Team design doc review meeting for the issue that CloudWatchMetricPublisher doesn't work well for lambda functions
+
+**Attendees:** Bole, David, Debora, Olivier, Dongie, Zoe
+
+**Closed Decisions:**
+
+1. Should we support a cw client in it? No, just writing to the logs is fine, if a cw client is needed then CloudWatchMetricPublisher is sufficient.
+2. Should we create a logger or take an instance of a logger? No, We should avoid taking a logger from the customer to prevent misconfiguration for now. We should also explore possible use cases and try it. Also, passing in the level of the logger might be a good idea. Logger.info is set as default logger level.
+3. Do we use jackson(easier but slower) (two way door) in the convert method? Yes, We can use third party Jackson-core in the convert method, because it is a two way door and we can try to implement different method and do performance test afterwards.
+4. Should we use SDK's LoggingMetricPublisher as alternative? No, the dealbreaker is that it is under core/metric-spi, we should separate the module from it.
+5. Should we use MetricLogger as alternative? No, it depends on jackson-databind, which is prone to CVEs.
+
+**Open Decisions:**
+
+None